The present invention relates to power trains, especially for use in motor vehicles. More particularly, the invention relates to improvements in power trains of the type wherein a prime mover (such as an internal combustion engine) and a transmission (such as a continuously variable transmission) flank an electric machine having a stator and a rotor surrounded by the stator and operatively connected or connectable with the rotary output member (e.g., a first shaft) of the prime mover and/or with the rotary input member (e.g., a second shaft) of the transmission.
Published German patent application Serial No. 196 25 022 discloses a power train wherein the electric machine is coaxial with the output member of the prime mover and is installed axially between the prime mover and the transmission. For example, the electric machine can be put to use during starting of the prime mover (such as a combustion engine) in the power train of a motor vehicle. Alternatively, the electric machine can act as a booster, i.e., to assist the prime mover in transmitting torque to the input member of a change-speed transmission in the power train of a motor vehicle not only during starting but also in actual use of the motor vehicle. Still further, the electric machine can form part of or it can drive a current generator (charging system). It is also possible to employ the electric machine as a means for controlling the transmission during deceleration of a motor vehicle (recuperation). In many instances, the electric machine can be activated (e.g., positively connected in or disconnected from the power train) in response to engagement or disengagement of one or more clutches.
The placing of an electric machine axially between the prime mover and the transmission is desirable in many instances because this often contributes to optimal operation of the power train. On the other hand, heretofore known power trains which employ an electric machine between the prime mover and the transmission are likely to exhibit the drawback that their space requirements (especially in the axial direction of the output member of the engine) are excessive. This creates problems when the power train is to be installed under the hood of a motor vehicle wherein the axis of the output shaft of the engine is to extend transversely of the direction of movement of the vehicle.
Conventional power trains of the above outlined character frequently employ dry friction clutches (for example, to disconnect the electric machine from the prime mover and/or from the transmission, or to cooperate with starter clutches) which will operate satisfactorily (i.e., which will reliably transmit a desired torque) only if the diameters of their friction linings exceed a certain threshold value. Such friction linings must be installed outside of the rotor of an electric machine, i.e., axially in line with rather than radially around or within the rotor of the electric machine.
An object of the instant invention is to enhance the compactness of power trains which utilize electric machines.
Another object of the invention is to provide a power train wherein the transmission can be placed into close or immediate proximity to a prime mover such as the internal combustion engine in the power train of a motor vehicle.
A further object of the invention is to provide a power train wherein the electric machine can perform any one of a host of different functions, such as the task of a starter generator, of a hybrid starter and/or of a generator for conversion of mechanical energy into electrical energy during deceleration of the vehicle.
An additional object of the invention is to provide a power train which can perform one or more of the above outlined functions with a minimum of space requirement, during extended periods of use, and by resorting to simple and compact but reliable controls.
Still another object of the invention is to provide a motor vehicle which embodies a power train of the above outlined character.
A further object of the invention is to provide novel and improved controls for use in conjunction with the above outlined power train.
An additional object of the invention is to provide a novel and improved combination of an electric machine and a variable-speed transmission and/or a combustion engine or another prime mover in the power train of a motor vehicle.
The invention is embodied in a power train which can be utilized with advantage in a motor vehicle and comprises a prime mover (e.g., an internal combustion engine) including an output member (such as a shaft) rotatable about a predetermined axis, a transmission having a rotary input member (such as a shaft which is coaxial with and is connectable with the output member of the prime mover), and an electric machine which is coaxial with the output member and is located axially between the prime mover and the transmission. The improved power train further comprises an operative connection between the electric machine and the prime mover and/or the transmission. The electric machine comprises a stator and a rotor which is disposed radially inwardly of the stator and, in accordance with a desirable feature of the invention, the transmission includes at least one constituent which is located radially inwardly of the rotor.
The transmission is or can be constructed and assembled to transmit torque to the wheels of a motor vehicle.
The electric machine is or can be operatively connected with the output member of the prime mover and/or with the input member of the transmission. The operative connection can comprise at least one shiftable clutch, and the at least one constituent of the transmission can include a reversing gearing.
In accordance with a presently preferred embodiment, the at least one constituent of the transmission includes or constitutes a planetary transmission (hereinafter called planetary). Such transmission can comprise a sun gear, an internal gear, a planet carrier, and at least one planet pinion mounted on the carrier and mating with the two gears. The carrier can be connected with the sun gear or with a stationary housing; the latter can constitute the case of the transmission.
The improved power train can further comprise a torsional vibration damping device which is or which can be installed in a power flow between the prime mover and the electric machine or in a power flow between the electric machine and the transmission.
The prime mover and/or the transmission can be provided with a support (e.g., a flange which is coaxial with the output member of the prime mover), and the rotor can be journalled on or in such support. At least one bearing, preferably an antifriction roller bearing, can be installed between the support and the rotor.
The power train can further comprise an at least substantially sealed enclosure which is provided radially within the rotor, and at least a portion of the at least one constituent of the transmission is then confined in the enclosure. The enclosure can be at least partially filled with a fluid bath, particularly an oil bath.
The transmission can comprise a continuously variable transmission (CVT), and the rotor of the electric machine is or can be coaxial with the input member of such transmission.
The at least one constituent of the transmission can constitute at least one clutch, e.g., a disc clutch (particularly a multiple-disc clutch). The means for engaging and disengaging the at least one clutch can include at least one piston which is movable in the axial direction of the output member of the prime mover. Such piston can form part of a hydraulic cylinder and piston unit. The aforementioned means for engaging and disengaging the at least one clutch can further include a source of pressurized fluid and means for regulating the flow of pressurized fluid from the source to the cylinder for the at least one piston. The source preferably contains a hydraulic fluid, and the regulating means can comprise one or more valves, e.g., one or more on-off valves and/or one or more proporal valve.
The at least one constituent can include a transmission ratio varying portion of the transmission, for example, of a transmission having a plurality of gear ratios.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved power train itself, however, both as to its construction and the modes of assembling and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.